This application relates to a fuel nozzle with a heat shield mounted within a centerbody to reduce stress levels at an inner air swirler attachment interface.
A fuel injector or fuel nozzle is utilized in a combustion section of a gas turbine engine to discharge an air/fuel mixture into a combustion chamber. The fuel nozzle includes a centerbody that defines a portion of a fuel passage. A heat shield is mounted to the centerbody within an air passage. Air is pre-swirled prior to being mixed with fuel via an inner air swirler (IAS) having a plurality of vanes, with the IAS being fixed to an inner surface of the heat shield. The IAS is fixed to the heat shield by brazing at radially outward tips of the vanes.
In a current attachment configuration between the heat shield and centerbody, the heat shield has a first end that is press fit into the centerbody and a second end that is not attached to the centerbody. The heat shield is directly attached to the centerbody by brazing at a location immediately adjacent the press fit at the first end. Another known mounting configuration has the press fit and heat shield attachment joint fixed to the second end, while the first end is not attached to the centerbody. In either of these configurations, an outer surface of the heat shield is in close proximity or contacts an inner surface of the centerbody along a substantial portion of the axial length of the heat shield such that there is minimal to no gap between the centerbody and the heat shield.
One disadvantage with these known mounting configurations is that at elevated temperatures there is insufficient ability for the heat shield to remain thermally isolated from radially adjacent components. This can result in higher thermal stress levels at attachment interfaces for components attached to the heat shield. For example, these higher thermal stress levels can cause undesirable cracking at the attachment interface between the IAS and the heat shield leading to premature component wear, which is not desirable. Thus, there is a need for a heat shield mounting configuration that reduces the adverse effects of thermal stresses.